1. Field of Invention
This invention relates to systems/methods for controlling upshifting as a function of a value indicative of vehicular gross combined weight (GCW) in vehicles equipped with automated transmission systems and electronic data links. In particular, the present invention relates to an automatic transmission control system/method for heavy-duty trucks or coaches equipped with an electronic databus carrying engine torque and other information, such as a databus conforming to the CAN, SAE J1922 and/or SAE J1939 protocol, wherein the control parameter indicative of GCW is a filtered, averaged value, often an average of 500 or more individual determination iterations, to minimize the effects of driveline torsionals, noise and the like, and wherein the GCW control parameter value is reset to a default value at power-up or the like.
More particularly, the present invention relates to a control wherein the default value is relatively high and wherein certain skip upshifts are inhibited until the actual GCW is validated with a degree of confidence.
2. Description of the Prior Art
In a heavy-duty truck or tractor-semitrailer vehicle, vehicle GCW may vary in a range of from about 10,000 pounds up to about 80,000 pounds or more, depending upon vehicle type and load. It is highly desirable to at least approximate current GCW and to provide this information to vehicle systems such as, e.g., an automated transmission system, a fleet management system, a variable suspension system, an onboard central tire inflation system (CTIS), an antilock brake system (ABS) or the like.
It is known in the prior art to provide various scale systems for vehicles wherein a control parameter indicative of vehicle weight, or at least of the weight of the vehicle load, may be measured. See, e.g., U.S. Pat. Nos. 4,714,122; 4,728,922; 5,014,206 and 4,839,835, the disclosures of which are incorporated herein by reference.
These systems required scale or other weighing systems which were costly to provide and/or maintain and were best suited for vehicles, such as garbage trucks or dump trucks, involved in special haulage applications, such as commercial refuse disposal or the like.
Methods/systems for calculating GCW as a function of engine/drivewheel torque and vehicle acceleration, as read from signals on a data link and/or outputted by various sensors, are known in the prior art. In one example, the GCW of a vehicle may be determined from known drive train characteristics (transmission ratio, axle ratio, tire radius, etc.), engine torque and vehicle acceleration measured at time t.sub.1 and t.sub.2 if and t.sub.2 are relatively close (within seconds). This may be expressed as: EQU GCW=(T.sub.1 -T.sub.2).div.((A.sub.1 -A.sub.2).times.C)
where:
T.sub.i =Wheel torque at time t.sub.i ; PA1 A.sub.i =Vehicle acceleration at time t.sub.i ; and PA1 C=Wheel rolling radius.div. gravity constant.
To minimize the effects of drivetrain torsionals, noise and the like, GCW is, preferably, determined during or immediately after completion of an upshift and the control parameter GCW.sub.CP is a running, filtered average of many individual iterations of GCW determination. While the above-described methods/systems are very effective, they are not totally satisfactory as, in certain circumstances, they may not be as responsive as desired to situations wherein vehicles have stopped to change their loading, such as, for example, by adding or unloading cargo, connecting or disconnecting a semitrailer taking on or discharging coach passengers, or the like.
Automated vehicular systems using GCW as a control parameter and/or having logic for determining GCW may be seen by reference to U.S. Pat. Nos. 5,272,939; 5,335,566; 5,487,005 and 5,490,063, the disclosures of which are incorporated herein by reference.
A system for resetting the highly filtered value of GCW upon sensing conditions indicative of (i) the vehicle being at rest and/or the highly filtered value (GCW.sub.CP) differing from a less-filtered test value (GCW.sub.TEST) by greater than a predetermined value may be seen by reference to U.S. Pat. No. 5,491,630, the disclosure of which is incorporated herein by reference.
When a vehicle is stopped and then restarted, the GCW value is typically set to a default value. If the default value is relatively low (45,000 pounds or less), upshifts will be undesirably inhibited until a more accurate value is established. If the default value is relatively high (180,000 to 300,000 pounds, by way of example), the logic may become undesirably aggressive in attempting skip upshifts.